The carbonylation of aryl bromide or aryl iodide to produce products such as an aryl aidehyde, acid or ester derivative is broadly known. U.S. Pat. No. 4,128,554 and U.S. Pat. No. 3,988,358 disclose the use of a palladium-containing catalyst system optionally containing a triarylphosphine. The use of an aryl chloride would offer economic advantages since the chloride is typically cheaper than the bromide or iodide. Catalyst systems for carbonylation of aryl chlorides are disclosed by a number of published European Patent Applications including EP 352167 wherein palladium-containing catalyst systems also include tertiary mono-phosphines. EP-A-238194 illustrates the use of a bidentate phosphine ligand such as 1,4-bis(diphenylphosphino)propane. EP-A-406848 shows aliphatic-and aromatic-substituted diphosphines used in conjunction with palladium. At least one of the monovalent phosphorus substituents is aliphatic.
Although these references do teach formation of aryl derivatives by carbonylation of aryl halides, and even aryl chlorides, it would be of advantage to have an improved process wherein aryl halides are carbonylated at attractive reaction rates.